Using Landsat and soil clay content to map soil organic carbon of oxisols and Ultisols near São Paulo, Brazil

Background The loess-paleosol sequence on the Loess Plateau has been considered an important paleoclimatic archive to study global climatic and environmental changes in the Quaternary. So far, little attention has been paid to the characteristics of soil organic carbon fractions in loess-paleosol sequences, which may provide valuable information for exploring the evolution of climate and environment in the Quaternary on the Loess Plateau. Methods In order to explore the significance of mineral-associated organic carbon to total organic carbon (MOC/TOC) ratios in the loess-paleosol sequence for reconstructing paleoenvironmental and paleoclimatic evolution in the Quaternary on the Loess Plateau, we selected a typical loess-paleosol profile in Chunhua county, Xianyang city, Shaanxi province, as the research object. The content of total organic carbon (TOC) and MOC/TOC ratio in each loess and paleosol layers of the Chunhua loess-paleosol profile were analyzed, together with the paleoclimatic proxies, such as soil grain size, CaCO3 content and their correlations with organic carbon parameters. Results The main results were as follows: (1) the total content of soil organic carbon and MOC/TOC ratios were generally higher in paleosol layers than in the underlying loess layers of the Chunhua loess-paleosol profile. Compared to total organic carbon content, MOC/TOC ratios changed more obviously in soil layers below a paleosol layer S8; (2) soil clay content and median grain size (Md (ϕ)) were higher in paleosol than in the underlying loess, while CaCO3 content showed an opposite tendency. In the Chunhua profile, the distribution characteristics of the three paleoclimatic proxies showed good indications of paleoclimate changes in the Quaternary; (3) in the Chunhua loess-paleosol profile, MOC/TOC ratios were positively correlated with clay content and median grain size (ϕ), while negatively correlated with CaCO3 content, and the correlations were more significant in soil layers below S8. Discussion Our results indicated that MOC/TOC ratios in the Chunhua loess-paleosol profile correlated with the cold dry-warm wet paleoclimatic cycle in the Quaternary. The high MOC/TOC ratios in the loess-paleosol profile might reflect warm and humid climate, while lower ratios indicated relatively cold and dry climate. That is because when the climate changed from warm-humid to cold-dry, the vegetation coverage and pedogenesis intensity decreased, which increased soil CaCO3 content and decreased soil clay content and Md (ϕ), leading to decreased MOC/TOC ratios. Compared to TOC, MOC/TOC ratios had greater significance in indicating paleoenvironmental evolution in the Quaternary on the Loess Plateau. Therefore, investigating MOC/TOC ratios in loess-paleosol profile can offer new evidence to reconstructing paleoenvironmental changes, and also provide a basis for predicting responses of soil organic carbon pools to vegetation and climate changes in the future.

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Linkage of microbial living communities and residues to soil organic carbon accumulation along a forest restoration gradient in southern China

Forest Ecosystems ◽

10.1186/s40663-021-00334-8 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Shuo Zhang ◽

Qi Deng ◽

Ying-Ping Wang ◽

Ji Chen ◽

Mengxiao Yu ◽

...

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Forest Restoration ◽

Southern China ◽

Total Phospholipid ◽

Soil Layer ◽

Clay Content ◽

Carbon Accumulation ◽

Stand Age ◽

Soil Clay Content

Abstract Background Forest restoration has been considered an effective method to increase soil organic carbon (SOC), whereas it remains unclear whether long-term forest restoration will continuously increase SOC. Such large uncertainties may be mainly due to the limited knowledge on how soil microorganisms will contribute to SOC accumulation over time. Methods We simultaneously documented SOC, total phospholipid fatty acids (PLFAs), and amino sugars (AS) content across a forest restoration gradient with average stand ages of 14, 49, 70, and > 90 years in southern China. Results The SOC and AS continuously increased with stand age. The ratio of fungal PLFAs to bacterial PLFAs showed no change with stand age, while the ratio of fungal AS to bacterial AS significantly increased. The total microbial residue-carbon (AS-C) accounted for 0.95–1.66 % in SOC across all forest restoration stages, with significantly higher in fungal residue-C (0.68–1.19 %) than bacterial residue-C (0.05–0.11 %). Furthermore, the contribution of total AS-C to SOC was positively correlated with clay content at 0–10 cm soil layer but negatively related to clay content at 10–20 cm soil layer. Conclusions These findings highlight the significant contribution of AS-C to SOC accumulation along forest restoration stages, with divergent contributions from fungal residues and bacterial residues. Soil clay content with stand age significantly affects the divergent contributions of AS-C to SOC at two different soil layers.

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Remaining phosphorus and sodium fluoride pH in soils with different clay contents and clay mineralogies

Pesquisa Agropecuária Brasileira ◽

10.1590/s0100-204x2004000300006 ◽

2004 ◽

Vol 39 (3) ◽

pp. 241-246 ◽

Cited By ~ 6

Author(s):

Marcelo Eduardo Alves ◽

Arquimedes Lavorenti

Keyword(s):

Buffer Capacity ◽

Ammonium Oxalate ◽

Clay Mineralogy ◽

Clay Content ◽

Response Curves ◽

Solution Ph ◽

Ph Values ◽

Soil Clay ◽

Soil Clay Content ◽

Discriminatory Capacity

The remaining phosphorus (Prem) has been used for estimating the phosphorus buffer capacity (PBC) of soils of some Brazilian regions. Furthermore, the remaining phosphorus can also be used for estimating P, S and Zn soil critical levels determined with PBC-sensible extractants and for defining P and S levels to be used not only in P and S adsorption studies but also for the establishment of P and S response curves. The objective of this work was to evaluate the effects of soil clay content and clay mineralogy on Prem and its relationship with pH values measured in saturated NaF solution (pH NaF). Ammonium-oxalate-extractable aluminum exerts the major impacts on both Prem and pH NaF, which, in turn, are less dependent on soil clay content. Although Prem and pH NaF have consistent correlation, the former has a soil-PBC discriminatory capacity much greater than pH NaF.

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P-sorption and desorption in Savanna Brazilian soils as a support for phosphorus fertilizer management

Ciência e Agrotecnologia ◽

10.1590/s1413-70542013000600005 ◽

2013 ◽

Vol 37 (6) ◽

pp. 521-530 ◽

Cited By ~ 17

Author(s):

Flávio Araújo Pinto ◽

Edicarlos Damacena de Souza ◽

Helder Barbosa Paulino ◽

Nilton Curi ◽

Marco Aurélio Carbone Carneiro

Keyword(s):

Clay Content ◽

Soil Characteristics ◽

Fertilizer Management ◽

Phosphorus Fertilizer ◽

Phosphorus Adsorption ◽

P Sorption ◽

Brazilian Soils ◽

Soil Clay ◽

Sand Base ◽

Soil Clay Content

Phosphorus (P) sorption by soils is a phenomenon that varies depending on soil characteristics, influencing its intensity and magnitude, which makes it a source or drain of P. The objective of this study was to determine the Maximum Phosphorus Adsorption Capacity (MPAC) and desorption of P from soils under native Savanna Brazilian and verify the correlation between MPAC and P Capacity Factor (PCF) with the chemical and physical properties of these soils. The study was conducted in seven soils under native Savannas. The Langmuir isotherms were adjusted from the values obtained in sorption assays, being evaluated the MPAC, the energy adsorption (EA) and PCF, which was calculated according to the levels of P-adsorbed and P-sorbed. Values of MPAC were classified as high in most soils, ranging from 283 up to 2635 mg kg-1 of P in the soil and were correlated with soil organic matter, clay, silt, sand, base saturation and pH. The PCF was higher in soils where the MPAC was also higher. The use of only one attribute of soil (clay content) as a criterion for the recommendation of phosphated fertilization, as routinely done, is susceptible to errors, needing the use of more attributes for a more accurate recommendation, as a function of the complexity of the interactions involved in the process.

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Surface soil clay content mapping at large scales using multispectral (VNIR–SWIR) ASTER data

International Journal of Remote Sensing ◽

10.1080/01431161.2018.1528018 ◽

2018 ◽

Vol 40 (4) ◽

pp. 1506-1533

Author(s):

Anis Gasmi ◽

Cécile Gomez ◽

Philippe Lagacherie ◽

Hédi Zouari

Keyword(s):

Surface Soil ◽

Clay Content ◽

Aster Data ◽

Soil Clay ◽

Soil Clay Content

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Factors Affecting Microbial Formation of Nitrate-Nitrogen in Soil and Their Effects on Fertilizer Nitrogen Use Efficiency

The Scientific World JOURNAL ◽

10.1100/tsw.2001.308 ◽

2001 ◽

Vol 1 ◽

pp. 122-129 ◽

Cited By ~ 7

Author(s):

Alan Olness ◽

Dian Lopez ◽

David Archer ◽

Jason Cordes ◽

Colin Sweeney ◽

...

Keyword(s):

Organic Matter ◽

Decision Aid ◽

Pore Space ◽

Organic Matter Content ◽

Clay Content ◽

Matter Content ◽

N Fertilizer ◽

Nitrate N ◽

Soil Clay ◽

Soil Clay Content

Mineralization of soil organic matter is governed by predictable factors with nitrate-N as the end product. Crop production interrupts the natural balance, accelerates mineralization of N, and elevates levels of nitrate-N in soil. Six factors determine nitrate-N levels in soils: soil clay content, bulk density, organic matter content, pH, temperature, and rainfall. Maximal rates of N mineralization require an optimal level of air-filled pore space. Optimal air-filled pore space depends on soil clay content, soil organic matter content, soil bulk density, and rainfall. Pore space is partitioned into water- and air-filled space. A maximal rate of nitrate formation occurs at a pH of 6.7 and rather modest mineralization rates occur at pH 5.0 and 8.0. Predictions of the soil nitrate-N concentrations with a relative precision of 1 to 4 μg N g–1of soil were obtained with a computerized N fertilizer decision aid. Grain yields obtained using the N fertilizer decision aid were not measurably different from those using adjacent farmer practices, but N fertilizer use was reduced by >10%. Predicting mineralization in this manner allows optimal N applications to be determined for site-specific soil and weather conditions.

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Boron adsorption in soils from the State of São Paulo, Brazil

Pesquisa Agropecuária Brasileira ◽

10.1590/s0100-204x2000000200020 ◽

2000 ◽

Vol 35 (2) ◽

pp. 413-421 ◽

Cited By ~ 15

Author(s):

LUÍS REYNALDO FERRACCIÚ ALLEONI ◽

OTÁVIO ANTONIO DE CAMARGO

Keyword(s):

Aluminum Oxide ◽

Correlation Coefficients ◽

Clay Content ◽

Sao Paulo ◽

The State ◽

São Paulo ◽

Aluminum Oxides ◽

Freundlich Isotherms ◽

Physical Attributes ◽

Boron Adsorption

Boron adsorption was studied in five representative soils (Rhodic Hapludox, Arenic Paleudalf and three Typic Hapludox) from the State of São Paulo, Brazil. Adsorption was higher in the clayey Oxisols, followed by the Alfisol and the coarser Oxisols. Calcium carbonate promoted an increase in the amount of adsorbed boron in all soils, with the most pronounced effect in the coarser-textured Oxisols. High correlation coefficients were found between adsorbed boron and clay and amorphous aluminum oxide contents and specific surface area (r = 0.79, 0.76 and 0.73, respectively, p < 0.01). Clay content, free aluminum oxide, and hot CaCl2 (0.01 mol L-1)-extracted boron explained 93% of the variation of adsorbed boron. Langmuir and Freundlich isotherms fitted well to the adsorbed data, and highest values for maximum boron adsorption were found in clayey soils, which were significantly correlated with contents of total, free and amorphous iron and aluminum oxides, as well with the physical attributes. Ninety four percent of the variation in the maximum adsorption could be related to the free iron content.

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Determination of the Environmental Factors that Affect the Growth and Survival of Greek Fir Seedlings

Land ◽

10.3390/land9040100 ◽

2020 ◽

Vol 9 (4) ◽

pp. 100

Author(s):

Vassilis Detsis ◽

Georgios Efthimiou ◽

Olga Theodoropoulou ◽

Stavroula Siorokou

Keyword(s):

Regression Model ◽

Mixed Model ◽

Linear Mixed Model ◽

Clay Content ◽

Weather Conditions ◽

Apical Growth ◽

Growth And Survival ◽

Initial Height ◽

Soil Clay ◽

Soil Clay Content

Forests in the montane-Mediterranean zone have only recently began to be affected by wildfires, therefore the knowledge necessary for restoration projects is missing. The aim of the study was to assess the effects of factors related to seedling attributes, weather conditions and site suitability on seedling performance. The characterisation of sites was based on bedrock and soil clay content as well as pre-fire vegetation. Apical growth and survival of seedlings was monitored for four years in Parnitha National Park. The parameters of a linear mixed model were estimated using annual apical growth of seedlings surviving in the end of the study as the dependent variable and type of site, rainfall, initial seedling height and age as explanatory ones. A quantile regression model using all the data available was estimated for each year of study, taking into account only initial height and site type as well as a logistic regression model of survival. The findings indicate that the growth of Greek fir seedlings depends on May rainfall mediated by soil clay content, which in turn depends on bedrock, which is consistent with the “inverse texture hypothesis”. Sites with low soil clay content were always more beneficial for survival, which was stronger affected by summer–autumn rainfall. In both contexts, drought stress due to soil clay content fades with increasing age. Sites that were not fir dominated prior to fire proved unsuitable also for planting fir seedlings. A minor part of the observed variability could be associated with the initial height of seedlings, especially for seedlings showing high rates of apical growth.

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